Deoxyribonuclease

Deoxyribonuclease (pronounced "dee-oxy-rybo-noo-clee-ase"),
or recombinant human deoxyribonuclease 1 (rhDNase or DNase), is an
experimental drug used to treat cystic fibrosis (CF), an inherited lung
disease. People with CF experience chronic (constant) and increasingly
worse symptoms throughout their lives. CF patients often die in their late
twenties. CF treatment has usually meant
antibiotics
and chest therapy (a physical pounding on the chest to loosen accumulated
fluids).

DNase

Scientists discovered that the mucus (slimy secretion) of CF patients is
full of DNA, which spills out of white blood cells as they die. DNase is
an enzyme (a protein-like substance) that cuts the DNA present in the
mucus. At first DNase was made from cows, but many patients had allergic
reactions to it. Then a company separated the gene for human
deoxyribonuclease, which chops up the protein but does not cause allergic
reactions.

DNase is delivered to the patient in
aerosol
form, and it improves lung function by breaking up the thick mucus in the
lungs. The patient is then able to clear the lungs by coughing. Considered
among the ten most important advances of 1993—the year the drug was
approved by the Food and Drug Administration (FDA)—it is also being
considered for the treatment of chronic bronchitis.

Cystic Fibrosis

An inherited (genetic) disease that affects about 1 out of every 2,000
Caucasians of European descent, cystic fibrosis (CF) is the leading
fatal genetic disease in the United States. CF occurs less frequently in
African Americans and very rarely in Asians and Native Americans.

The disease causes a thick mucus to accumulate in the lungs, pancreas,
and intestine. If the mucus blocks the lungs, the patient can die.
Pneumonia, caused by bacterial infections, is a common problem for CF
sufferers. People with CF suffer with abdominal (stomach) cramps,
malnutrition, growth retardation, and coughing.

Other serious complications common in people with cystic fibrosis
include respiratory (breathing) failure, diabetes, enlarged heart, liver
cirrhosis (a disease in which liver cells are destroyed), intestinal
blockage (bowel obstruction), pancreatic dysfunction (blocked ducts of
the pancreas, preventing digestive
enzymes
from leaving the pancreas), sterility (inability to have children), and
sodium (salt) deficiency. The increased saltiness of sweat is a highly
useful test to diagnose CF, since predicting when any of these symptoms
will appear or how severe they will be is a difficult task. Cystic
fibrosis used to be fatal to nearly all children who developed it, but
now more than 50 percent of CF patients live longer than 20 years.

Antihistamines
and decongestants aid breathing by helping to open air passages.
Antibiotics treat the pneumonia that often results from repeated lung
infections. Physical therapy and surgery play roles in managing CF.
Cough suppressants are avoided since coughing helps to loosen the mucus
in the trachea and lungs. Newer treatments, such as DNase and
gene therapy,
have given mixed results.